Electric fluid heater



Feb. 22,' 1949. H. c. INMAN ELECTRIC FLUID HEATER Filed May 12, 1947 2 Sheets-Sheet &vue/whom flaZZz's fnmn Feb. 22, 1949. H. c. lNMAN ELECTRIC FLUID HEATER 2 Sheets-Sheet 2 Filed May 12, 1947 Patented Feb. 22, 1949 UNITED STATES PATENT OFFICE ELECTRIC FLUID HEATER Hollis Chbbuck Inman, Miami, Fla.

Application May 12, 1947, Serial No. *747,431

Claims.

This invention relates to a heating unit for heating fluid, in either lquid or gaseous form.

More specifically, the invention relates to a fluid heating apparatus or unit including electrical heating means of the resistance type adapted to eifect heating of the fluid as it passes therethrough.

The present invention constitutes an improvement over the fluid heating units disclosed in my copending application Serial No. 621,?40, filed October 11, 1945.

The principal object of the invention is to provide heating means adapted to be connected in a pipe line to heat a liquid or gas as it is owing therethrough; or to be associated with a storage tank or boiler as a side arin heater or as an immersion heater, to heat the fluid in said storage tank or boiler.

A more specific object of the invention is to provide an eiiicient and economical electrical heating unit, particularly adapted for heating water for domestic or industrial use.

Still another object of the invention is to pro- Vide an immersion electric heating apparatus of the resistance type that will quickly provide a supply of heated liquid without requiring the heating of a comparatively large body of liquid in a storage tank or boiler.

A further object of the invention is to provide a liquid heating apparatus for association with a storage tank and including thermally responsive means for automatically maintaining the liquid in said storage tank at a predeternined temperature.

A still further object of the invention is to provide liquid heating apparatus consisting of parts made of material (preierably copper) having the same coefficient of thermal eXpanson so that all joints are relieved of undue Stress and strain and all leals due to unequal expansion of the parts are avoided.

Other objects oi the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Fig l is an enlarged side elevational View of one form of heating unit embodying the principles of the present invention, shown associated with a storage tank as a side arm heater;

Fig. 2 is an enlarged vertical sectional View through the heating unit shown in Fig. 1;

Fig. 3 is a sectional plan View through the heating unit taken on the line 3-3 of Fig. 2;

Fig. 4 is a vertical sectional View through a modified. form of heating unit embodying the principles of the invention and adapted to serve as an immersion type of heater;

Fig. 5 is a diagrammatic view illustrating the manner in which the immersion type of heater of (i may be mounted upon the upper end of storage tank; and

(i is a View similar to Fig. 5, diagrammatically iliustrating the manner in which the heating unit of Fig. i may be mounted upon the lower lid of a storage tenk.

Referring now to Figs. l to 3, inclusive, of the drawings, the fluid heating unit is generally identified by the numeral i& and comprises a central, cylindrical upright copper tube or duct ll, a Copper casing 2 arranged in concentric spaced relation relative to said tube and a Copper jacket !3 similarly arranged relative to said casing. The tube il cbvicusly may be connected in a pipe line (not shown) and. used without a storage tank, or the upper end of the tube ii may be connected to one end of a pipe !5 having its opposite end connected with the upper end of a storage tani; l6, and the lower end of said tube may be connected to one end of a pipe l'l having its opposite end connected with the lower end of the storage tank 58. A cold water supply pipe iii and a hot water service pipe 39, respectively, are connected to the upper end oi the storage tank iii. The lower end of the cold water supply pipe ae prefe'ably extends to a point near the lower end of the tank is so that a strata or cap of heated water will always be available for withdrawal through the hot water service pine !5, as will be explained in further detal later.

The casing i (Fig. 2) has an annular copper closure member at the upper end thereof and a similar closure member at the lower end thereof, The closure members 2% and 2! surround the tube i i and are turn surrounded by the casing iii, the parts being soldered, brazed or otherwise honded to provide a leakproof heating cornpartrnent 222 surrounding the tube il. A covering oi conventional heat resisting, electric insulating material preerabiy a preformed tube of niica and hinder, is slipped onto and closely surrounds the tube il within the compartment 22. Resilient clamping bands or rings 24 and 25 are arranged adjacent the opposite ends of the mica tube 23 and these clamping rings are split and seli-contractible for retaining themselves in place around the mica tube 23, as indicated by way of example in Fig. 3. The clamping ring 2 may be made of tempered steel, spring brass, or any other suitable spring material and carries contact lugs 2? and 28. Likewise, the clamping ring 25 may be made of similar material and carries contact lugs 29 and 30.

A resistance coil type of heating element 3! is helically wound upon the outer surface of the mica tube 23, and one end thereof is suitably secured to the lug 28 on the ring 2:3 and its opposite end is suitably secu'ed to the lug 33 on the ring 25. The heating element 3! is preferably made of "Nichromej' but may be made of any other con- Ventional or suitable material capable of developing high heat upon the passage of electric current therethrough. In any event, the heating coil 3! is prefer ably covered with a layer of fiber glass 32, which is a well known heat resisting, electrical insulating material. The clamping rings 24 and 25 anchor the heating coil 3! against the normal pull of said coil as it expands and con tracts upon heating and cooling.

The jacket !3 is of larger diameter and greater length than the casing Z, as will be apparent from Fig. 2, and is closed at its upper end by an annular copper closure member 33 and is closed at its lower end by a similar closure member 3 5. The closure members 33 and 3@ are soldered, brazed, or otherwise Secured to both the tube H and the jacket 33 to provide a leakproof fluid passage 35 surrounding the casing 12. A cylindrical copper sleeve 35 is disposed in aligned openings 37 and 38 formed in the casing [2 and the jacket i3, respectively, and is Secured thereto by soldering, brazing, or other means to provide a fluid-tight connection therewith. A heatresistant scaling member 39 is mounted in the sleeVe 36 and conductors or lead wires 453 and :ti eXtend through said member. One end of the conductor te is Secured to the contact lug 2@ on the ring 25 and its opposite end is secured to a contact 42 on a manu-any operable switch is. One end of the conductor ii is secured to the contact lug 2? on the ring ?e and its opposite end is secured to a conventional or suitable, adjustable thermostat M. Another conductor 55 connects the thermostat :34 with a contact 35 on the switch 43.

The thermostat 44 is mounted in a cylindrical portion 47 of a housing se, which may be made of copper and secured in thermal contact with the jacket 13 so that said thermostat is responsive to the temperature of the water in the jacket space 35. The housing se is enlarged at its lower end 49 to receive the switch 33 as indicated, and also serves as a housing for said switch. Th lower housing portion AQ has a Conduit 59 secured thereto through which extend leads 5! and 52 connected with contact means 53 for supplying electrical current to the switch 43, as is well understood.

The tube li has openings 5 located at a point between the closure members 25 and 33, in order to establish communication between the interior of said tube and the upper end of the fluid space 35, and openings 55 located between the closure members ZI and se to establish communication between the interior of said tube and the lower end of said fluid space.

In the normal operation of the device illustrated in Figs. 1 to 3, the water to be heated passes from the lower end of the storage tank i& through the pipe I' into the lower end of the unobstructed tube I I and flows through said tube as a central stream. The major portion of the water entering the tube i! Will pass directly therethrough, but a substantial portion will be diverted or diverge through the openings 55 and pass into the jacket iS for flow through the space 35 in the form of an annular stream in contact with the exterior of the casing !2. The water diverted into the jacket space 35 again re-enters or converges with the central Stream in the tube li by passing through the openings 54. Thus, the divergence of water from the central stream into the annular stream and the convergence of water from the annular stream into the central stream are the same at both ends of the unit.

Assuming that the switch is in closed posir tion, electrical current will pass through the ter and the static head of hot heating coil 3! with the result that intense heat will be produced thereby. This heat will pass through the mica insulation 23 and be transmitted by the tube H directly to the water flowing through the same. Simultaneously, some of the heat thus produced will pass through the insulation material 32 and the air within the chamber 22 and be conducted by the casing !2 to the water in the jacket space 35, whereby to heat the fluid diverted into said space. The heating coil ti extends for a considerable distance along the length of the tube I i so that as the fluid flows npwar'liy therethreugh, and upwardly in the jacket space 35, it is progressively heated and is quite hot by the time it reaches the upper end of said tube.

If the heating device m is connected in a separate pipe line (not shown) the water thus heated is ready for instantaneous use. On the other hand, if the heater iii is associated with a storage tenk IS, as previously described, the heated water emerging from the upper end of the tube II will pass through the pipe !5 into the upper end of said storage tank and form a "cap" or stratum of heated water which progressively increases in depth without substantial turbulence. This cap" provides heated water which is available for imiediate withdrawal through the hot water service pipe 59. Circulation is normally induced between the storage tank it and heater n by thermal action, which causes the relatively cooler water at the lower end of the storage tank IS to flow into the heater i& and to be discharged therefrom into the upper end of said storage tank.

Experiments have shown that hot and cold Water in the same heating system constantly seek their own levels and hence, for any given static head of hot water in the tank !5 there will be a corresponding static head of hot Water in the jacket space of the heater !9. The foregoing is true notwithstanding the fact that there is a free flow of water between th heater ll] and storage tank !5. Accordingly, the head of the hot water in the jacket space 35 Will reach a depth sufiicient to efiect actuation of the thermostat 34, Whereupon the flow of current to the heating coil sa will be interrupted, as will be readily understood, and heating of the liquid Will be discontinued. It will also be apparent that as the heated Water is Withdrawn from the storage tank i@ it will be replaced by relatively cool wa- Water will change in the tank l 5 and in the jacket space 35, thereby efi'ecting actuation of the thermostat 34 in a manner such that the circuit to the heating coil 3! will be closed and current will flow through said coil to eect heating of the water, as previously described.

The purpose of the fluid space 35 is to absorb the heat that is radiated outwardly from the heating coil %i through the casing !2, and which would otherwise be lost to the surrounding air 2,4ca74c and result in ineflicient operation of the heater. Hence, the provision of the fluid space t surrounding the casing !2 results in econcmy and eicient operation and also maintains the heating coil 3! at a relatively low temperature. Heat losses through the jacket i3 are practically negligible so that it is unnecessary to heat insuiate jacket, although such insulation may be provided if a maximum of economy is desired.

Fig. i illustratcs a heater generally identified by the numeral Ec ernhedying certain of the structural features of the heater shown in Figs. 1 to 3, but modified so that it can serve as an immersion type of heater. The heater iii comprises a cylindrical Copper casing having its upper end snugly received in a recess 52' formed in a Copper plug 58. The casing is soldered, brazed, or otherwise Secured in fiuid tight relation to said plug. The exterior of the plug is threaded and mounted in a correspcndingly threaded opening 59 formed in the upper end of a storage tank se (Fig. 5). A Copper tube ti is arranged concentrically in. the casing and an annular copper closure member is scldered, brazed, or otherwise Secured in fiuidtion to both the tube &i and the the lower end of said casing. The tube has an upper end 53 which extends at a right angle to the main body portion of said tube projects through an opening 64 iormed the side of the casing 56. The upper end 63 of the tube E! is soldered, brazed, or otherwise secured the opening 64 so that here again a uid-tight connection is provided. The tube closure member 62, and the plug are thus assembled to form a conpartment 6:5 which sealed against the entrance of any water thereinto. The portion of the tube 5! within the ccmpartment 65 is covered, as indicated at for substantially its entire length, by mica (sii 'lar to the covering 23) and is held in place by cla '113- ing rings 6'! and 68 similar to the clamping rings 2 1 and 25. The clamping ring E? carries contact lugs 59 and 'lil and the clamping ring carries contact lugs 'li and '32. A heating coil of the resistance type, similar to the heating coil is wound around the mica covering t & and one end thereof is Secured to the contact 59 and ti end is Secured to the contact 12. A body of sealing material 'M is mounted in an opening ormed in the plug 53, and lead wires "iii extend therethrough and into the chamber One end of the lead wire 16 is connected with the contact 'MJ and one end of the lead wire 'E'i is connected with the contact 'l i. The opposite erds of the lead wires 16 and 'H are connected with a thermostat M and switch 43 to the thermostat t and switch 43, mounted in a housing 48% similar to the housing cs alread, described in detail, mounted on the outside of the tank 60.

Referring to Fig. 5, a cold water inlet pipe and a hot water service pipe 19, respectively, are connected to the upper end of the storage tenk se. The arrows in Fig. 5 indicate the movement of the water within the storage tank Thus, the heat produced by the heating coil 'is causes a thermal circulation of the water within the storage tank fil] such that relatively cool water enters the lower end of the tube si and flcws upwardly through said tube for discharge through the upper end 63 thereof at a point ad acent the uppermost portion of the storage tank fil so that a "cap" of hot liquid is always available for with drawal through the hot water service pipe 19.

t rela- The water .fiowing through the tube fil is heated by the heat conducted there'to through the tube ti, and the body of water surrounding the casing ii is heated :by the heat conducted thereto through the casing 55, so that none of the heat prcduced by the coil 13 is lost and the heating unit iii thereore operates at a very high effciency.

Fig. 6 is a diagrarnmatic View sornewhat similar to Fig. 5, but shows the plug 58 mounted in the lower end of astorage tank Gt instead of in the upper end of the tank as in Fig. 5. In Fig. 6, the thermally induced circulation of the water withinthe tank occurs upwardly through the tube ti, the water entering through the tube end 63 and fiowing upwardly for discharge at a point adjacent the upper end of the tank 60 The transfer of the heat to the water in. Fig. 6 occurs 'the same manner as that described in connecn with Fig. 5. The tank'fl of course, is prov d with a cold water inlet pipe 18 and a hot water service pipe ie Thus, irrespectlve of whether the immersion heater !t is mounted in t e top or in the bottom of a storage tank, the

it will cperate at 'high efficiency without ap- L -ecable heat loss.

In. ail embcdiments of the invention disclosed herein, the winding of the heating coil with its conv oiutions uniiormiy spaced throughout the near full length oi the central duet provides a convenient way to control the distribution or concentration of the intense heat produced by heating coil. Moreover, by surrounding the hea'- ig chambers with the fluid to be heated, a higher rate of heat abscrption by the fluid, and an extremely comparatively low coil temperature, are obtained, resulting in a long life of the heat ing coil and in a minimum of solids deposited upon. the heat transfer surfaces of the heating units. In addition, by discharging the heated water into the top of the storage tanks, a heated "cep" of fluid is formed as shown by the dotted lines in Figs. l, 5 and 6, which progressively increases in depth as the water isheated. This is accomplished without mixture or turbulence between the hot and cold water so thata maximum temperature is maintained in the body of heated water as against an average temperature obtained in other types of heaters.

It will he understood that various changes may he nja-de in the details of Construction and in the arrangement of the parts of the heating units i .losed herein, without departing from the g of the invention or the scope of the annexed cla ms.

I claim:

l. A fluid heater. comprising: a tubular duct providing a passage for a central fluid stream; a casing providing an elongated closed chamber surrounding said tubular duet; electrical heating means in said charnber; and a jacket surroundtubular duct and enclosing said casing jacket being 'of greater length and greater transverse dimension than said casing and providing an annular fluid space about the periph ery and ends of said casing for an annular fluid stream, said tubular duct having identical openings establishing communication between the interior thereof and the spaces in said fluid jacket at the respective ends of said casing, whereby the divergence of fluid from the central fluid stream into the annular fluid stream and the convergence of fluid from the annular fluid stream into the central fluid stream are the same at both ends of the heater.

2. A fluid heater, 'ornprising: a asig; a tube for fluid to be heated, said tube providing a passage for a central fluid stream and being of smaller diameter than said casing and extending axially of said casing and providing an annular space for a heating element between said tube and casing; a covering of heat insulating mate- 'rial surrounding said tube within said casing; a metal band at each end of said ccvering securing .said covering in place around said tube; a helical resistance heating element in said casing surrounding sai-d covering and having its opposite ends connected to said bands; a lead wire connected to each of said bands; and a jacket surrounding said tube and enclosing said casing, said jacket being of greater length and greater transverse dimension than said casing and pro viding an annular fluid space about the periphery and ends of said casing for an annularfluid stream, said tube having identical openings estab-li-shing communication between the interier thereoi and the spaces in said fluid jacket at the respective ends of said casing, whereby the divergence of fluid from the central fluid stream into the annular fluid stream and the convergence of fluid from the annular fluid stream into the central fluid stream are the same at both ends of the heater.

3. A fluid heater, comprising: a central tube providing a passage for a central fluid stream; a casing surrounding said tube and being closed at its opposite ends; a jacket surrounding said tube, said jacket being of greater diameter than said casing and of greater length than said sasing, and being closed at its opposite ends to provide an annular space for an annular fluid stream surrounding said tube and casing, said tube having identical openings establishing communication between the interier thereof and the interlor of said jacket at points located outwardly' of the ends of 'said casing, whereby the divergence of fluid from the central fluid stream into the annular fluid stream and the convergence .of fluid from the annular fluid stream into the: :central fluid stream are the same at both ends: :of the heater; a circuit including electrical beat- :ing means in said casing for simultaneously heat- :ing fluid in said tube and in said jacket; and a. :thermostat in said circuit responsive to the temperature of fluid in said jacket co-ntrolling the supply of current to said heating means.

4. A fluid heater, comprising: a tubular duct providing a passage for a central fluid stream; :a cylindrical casing arranged concentric with said duct; closure members for said casing at the opposite ends thereof engaging said tubular duct and forming an elongated closed chamber surrounding said tubular duct; electrical resistance heating means in said chamber; a cylindrical jacket arranged concentrically with said casingz, said cylindrical jacket being of greater diameter and greater length than said casing; closure members at the ends of said jacket engaging said tubular duct and forming a sealed fluid e chamber for' an annular fluid stream about said casing, said tubular duct having identical openings establishing communication between the interior thereof and 'said fluid chamber, whereby the divergence of fluid from the central fluid stream into the annular fluid stream and the -ccnvergence of fluid from the annular fluid stream into the central fluid stream are the same at both ends of the heater, said casing and jacket having aligned openings at one side thereof; a sleeve mounted in said openings and bridging said fluid chamber at said one side; and lead Wires extending through said sleeve and connected with said electrical resistance heating means.

5. A fluid heater having uniform thermal ex pansion, comprising: a Copper jacket; a Copper casing of shorter length and smaller diameter than said jacket disposed concentrically within said jacket and spaced therefrom to provide an annular fluid passage therebetween; a tubular cop-per duct of smaller diameter than said casing extending through said jacket and casing and providing an annular space between said casing and said tubular duct, said tubular duct having a central passage for a central fluid stream; copper closure members a'djacent the cpposite ends of said casing converting said annular space into a heating compartment surrounding said tube; `Copper closure members between said tube and he ends of said jacket converting said annular fluid space into a passage for an annular fluid stream, said tubular duct having identical openings therein located at a region between the 'closure members at the ends of said casing and the closure members at the ends of said jacket establishing communication between the interior of said duet and said annular fluid passage, whereby the divergence of fluid from the central fluid stream into the annular fluid stream and the convergence of fluid from the annular fluid stream into the central fluid stream are the same at both ends of the heater; a covering of mica surrounding said tube in said heating eompartment; and electrical resistance heating means wound upon said mica covering in said heating compartment for simultanecusly heatfluid in 'said tubular duct and in said fluid compartment.

HOLLIS CHUBBUCK INMAN.

REFEREN CES CITED The following references are oi record in the flle of this patent:

UNITED PATENTS Number Name Date l,445,919 Stone Feb. 20, 1923 l,45l,863 Clark Apr. 17, 1923 11614974 Strauss Jan. 18, 1927 1,674369 McQuinn June 19, 1928 1,723,733 I-Iyde et al. Aug. 6, 1929 1,780,426 Hyde Nov. 4, 1930 1,'9943765 Harvey Mar. 19, 1935 

